Hydraulic pump controller for construction machine

Abstract

A hydraulic pump controlling apparatus of a construction machine according to the present disclosure includes: a hydraulic pump in which a swash plate angle is controlled to control a discharge flow; an auxiliary pump; a control valve controlling a flowing direction of a fluid discharged from the hydraulic pump and selectively supplying the fluid to an actuator; an orifice and a relief valve connected between a center bypass line of the control valve and a tank T to be parallel to each other; signal pressure selecting units receiving a fluid passing through the center bypass line of the control valve and a fluid discharged from the auxiliary pump, and selecting the pressure of any one of the fluids as a signal pressure; and a regulator receiving the signal pressure selected from the signal pressure selecting units to control the swash plate angle of the hydraulic pump, and the signal pressure selecting unit selects the pressure of the fluid discharged from the auxiliary pump as the signal pressure and transfers the selected pressure to the regulator when the construction machine is in an idle state.

The invention claimed is: 
     
       1. A hydraulic pump controlling apparatus of a construction machine, comprising:
 a hydraulic pump in which a swash plate angle is controlled to control a discharge flow; 
 an auxiliary pump; 
 a control valve controlling a flowing direction of a fluid discharged from the hydraulic pump and selectively supplying the fluid to an actuator; 
 an orifice and a relief valve connected between a center bypass line of the control valve and a tank (T) to be parallel to each other; 
 signal pressure selecting unit receiving a fluid passing through the center bypass line of the control valve and a fluid discharged from the auxiliary pump, and selecting the pressure of any one of the fluids as a signal pressure; and 
 a regulator receiving the signal pressure selected from the signal pressure selecting units to control the swash plate angle of the hydraulic pump, 
 wherein the signal pressure selecting unit selects the pressure of the fluid discharged from the auxiliary pump as the signal pressure and transfers the selected pressure to the regulator when the construction machine is in an idle state. 
 
     
     
       2. The apparatus of  claim 1 , wherein the signal pressure selecting unit includes:
 a valve unit changed between a first position where the pressure of the auxiliary pump is transferred to the regulator and a working fluid of the center bypass line is discharged to the tank (T) and a second position where the pressure of the center bypass line is transferred to the regulator; and 
 a controller changing the valve unit to the first position when a work signal (P i ) is not inputted and changing the valve unit to the second position when the work signal (P i ) is inputted. 
 
     
     
       3. The apparatus of  claim 2 , wherein the valve unit includes:
 a first valve passing or interrupting a pilot working fluid of the auxiliary pump according to a signal of the controller; and 
 a second valve transferring a pilot pressure of the auxiliary pump passing through the first valve to the regulator and discharging the working fluid of the center bypass line to the tank (T) when the first valve is at a position to pass the pilot working fluid of the auxiliary pump and transferring the pressure of the center bypass line to the regulator when the first valve is at a position to interrupt the pressure of the pilot working fluid of the auxiliary pump. 
 
     
     
       4. The apparatus of  claim 3 , further comprising an auxiliary relief valve discharging the pilot working fluid of the auxiliary pump to the tank (T) when the pilot pressure of the auxiliary pump is equal to or higher than a reference pressure. 
     
     
       5. The apparatus of  claim 1 , wherein the signal pressure selecting unit includes:
 a shuttle valve transferring the larger pressure between the pilot pressure of the auxiliary pump and the pressure of the center bypass line to the regulator; 
 a control valve installed between the center bypass line and the tank (T) to be parallel to the orifice and the relief valve to connect or interrupt the center bypass line to or from the tank (T); and 
 a direction switching valve connecting the shuttle valve to the auxiliary pump or connecting the shuttle valve to the tank (T), 
 wherein the control valve and the direction switching valve are changed depending on the pressure of a valve signal line varying depending on the change of the control valve, 
 the control valve connects the center bypass line to the tank (T) when the control valve is in a neutral state and interrupts the connection between the center bypass line and the tank (T) when the control valve is not in the neutral state, and 
 the direction control valve connects the shuttle valve to the auxiliary pump so that the shuttle valve selects the pressure of the auxiliary pump when the control valve his in the neutral state and connects the shuttle valve to the tank (T) so that the shuttle valve outputs the pressure of the center bypass line when the control valve is not in the neutral state. 
 
     
     
       6. The apparatus of  claim 1 , wherein the signal pressure selecting unit includes:
 a signal pressure selecting valve changed so that the auxiliary pump his connected to the regulator and the working fluid of the center bypass line is discharged to the tank (T) when a pressure receiving portion is connected with the auxiliary pump and changed so that the connection between the auxiliary pump and the regulator is interrupted and the center bypass line is connected to the regulator; and 
 a direction switching valve connecting the pressure receiving portion of the signal pressure selecting valve to the auxiliary pump or the tank (T), 
 wherein the direction switching valve is changed according to the signal pressure of the valve signal line in which the pressure varies depending on the change of the control valve, and 
 the direction switching valve connects the pressure receiving portion of the signal pressure selecting valve to the auxiliary pump when the control valve is in the neutral state and connects the pressure receiving portion of the signal pressure selecting valve to the tank (T) when the control valve is not in the neutral state.